As a mid-level indie rock group, Headlights have played their share of sparsely attended shows — club gigs where no one shows up, opening spots where the dozen or so people in the audience make small talk over Old Styles while waiting for the headliner to show up. But still, I felt a little embarrassed when Headlights walked on stage in the Louis Room on Friday to play for a crowd of about 35, especially when they have a history of selling out their Chicago shows. Sure, Niteskool’s publicity push for the event seemed a little low-key and most NU students haven’t heard of Headlights, but still — they had a song on Grey’s Anatomy! That counts for something, right?

The band took the low turnout like the touring champs they are, though. You get a sense that they’ve done this so many times, and the five members know each other so well, that they could play for an empty room and still produce a sound as warm and engaging as they did Friday night. In fact, for the first few songs, you got an impression that that’s what was happening on stage: From Erin Fein’s close-eyed chirping to Tristan Wright looking down and fiddling with his guitar, Headlights focused entirely on playing their flawless pop songs flawlessly, without paying much attention to who was watching. But as the set went on, the band started looking outward more and found that the three dozen people who did show up were actually a pretty good audience, with dance circles breaking out at the sides of the crowd and the rest of the watchers paying hushed, head-nodding attention.

Headlights’s brand of nostalgia-soaked boy/girl twee comes across as surprisingly muscular in concert, as do the band’s members. I spotted tattoos on three out of five of them, and singer Tristan Wright’s trucker hat, big arms and sideburns made him look more suited for a spot in an SoCal punk group than an indie-pop act. That fact, of course, just made the crooning about childhood streets and disputes with landlords more genuine: There’s no affect to Headlights. The only agenda is pretty, well-played music. At a few points in the concert, the members seemed inexplicably happy, throwing beaming glances at each other. It might have just been because they were having a good time or might have been because they had just remembered some joyous, shared experience. While the rest of Northwestern was engaged in whatever the rest of Northwestern does on a Friday night, the 40 or so people in the Louis room — band and audience — got to enjoy the simple, awesome pleasure of some nice songs executed perfectly.

As for Butterfly Assassins, the opener featuring Northwestern’s own Danny Yadron on bass: They played really well. It’s clear the five members of the band take what they do very seriously, tightly recreating the band’s baroque collective-rock (yeah, I’m making up a word to describe bands that sound, act and dress like the Arcade Fire). The histrionic vocals, kinda long songs and all that squalling-guitar, swelling-violin bombast might not appeal to everyone, but Friday night there was no denying that the songs contain some moments that explode with energy, rocking hard enough to make you forget that this isn’t their full-time job — yet.